Automatically enter the timestamp for the latest update on the current Google spreadsheet.

timestampOnEdit.js

const RECORDING_SHEET_NAME = 'SHEET_NAME'; // Sheet name to record the timestamp.
const RECORDING_CELL = {'row': 2, 'column': 2}; // Row and column number of the cell to record the timestamp.

/**
 * Automatic timestamp for the latest update on this spreadsheet.
 */
function onEdit() {
  var now = new Date();
  var timestamp = now.toISOString();
  SpreadsheetApp.getActiveSpreadsheet()
    .getSheetByName(RECORDING_SHEET_NAME)
    .getRange(RECORDING_CELL.row, RECORDING_CELL.column)
    .setValue(timestamp);
}